A dental implant, which means implanting an artificial tooth, implants a fixture, which is a dental root formed of titanium that does not have rejection symptoms against a human body, into an alveolar bone from which a tooth is pulled out, so as to replace a lost dental root, and then fixes the artificial tooth thereon to recover a function of an original tooth. The dental implant does not damage a periodontal tissue, has the same function and shape as those of a natural tooth, and does not cause dental caries, such that the dental implant may be semi-permanently used. Therefore, implant treatment has recently increased rapidly.
The implant is various depending on a kind of fixture, but is generally completed by drilling an implantation position using a predetermined drill, implanting the fixture into the alveolar bone to osseo-integrate the fixture into the alveolar bone, coupling an abutment onto the fixture, and then covering the abutment with a final prosthesis.
The implant includes the fixture implanted as an artificial dental root, the abutment coupled onto the fixture, an abutment screw fixing the abutment to the fixture, and an artificial tooth coupled to the abutment. Here, before the abutment is coupled onto the fixture, that is, during a period in which the fixture is osseo-integrated into the alveolar bone, a healing abutment (not illustrated) is coupled to the fixture, and is maintained in a coupled state.
In addition, the fixture, which is a portion implanted into an implantation hole formed in the alveolar bone using a drill, or the like, at a position at which implant treatment is to be performed, serves as the artificial dental root, and includes a fixture body and a screw portion (corresponding to a threader of the present invention) formed on an outer surface of the fixture body.
The screw portion is inserted into the alveolar bone to allow the fixture and the alveolar bone to be firmly coupled to each other and increase a contact area between the fixture and alveolar bone, thereby serving to enhance fixing force of the fixture for the alveolar bone.
In FIG. 4, an implant fixture according to the related art is illustrated.
The implant fixture 100 includes a body portion 110 having a screw thread 111 formed at the same size from an upper end thereof to a lower end thereof and an entry portion 120 disposed at a lower side of the body portion 110 and having a cut groove 121 formed at an outer portion thereof. In the implant fixture according to the related art described above, there is a tendency that a torque aspect appearing at the time of insertion by repetitive rotation of the implant fixture initially rises and is then gradually decreased, such that initial fixing force is decreased. Therefore, the implant fixture should be compressed, pushed, and fixed into the alveolar bone. As a result, a bone cure is delayed, and when occlusal force (masticatory force) is generated after the bone cure, shear force is generated between a thread and the alveolar bone, such that the alveolar bone is prone to fracture, and a difference in a strength and an elasticity degree between the thread and the alveolar bone is not considered, such that it is likely that the alveolar bone will fracture.
In addition, since the screw thread has a triangular cross section of which tips are sharp, it is easily inserted at the time of rotation, but is compressed to the alveolar bone in a vertical direction by an inclined surface as well as in a horizontal direction, such that there is a risk that the alveolar bone will be damaged, and a large amount of bone fragments are generated.
Therefore, there is a need to develop a new fixture capable of preventing fracture of the alveolar bone and minimizing a compression strength and generation of a stress when the occlusal force is applied by considering differences between a strength and an elasticity degree of the screw thread of the fixture formed of titanium and a strength and an elasticity degree of the alveolar bone.